来自《耶鲁大学开放课程：基础物理 第10集 第10集》

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  You guys should think about what does this quantity stand for?
  你们想想这个量代表什么
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  Can you tell me what it stands for?
  你能告诉我这个代表什么吗
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  Yeah.
  请讲
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  Yeah, by that it means,
  是的 它意味着
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  if you're really traveling with the center of mass,
  如果你的确随着质心运动
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  and you made a measurement on how fast every body's moving,
  然后测出每个个体的运动速度
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  this is the energy you will attribute to these particles.
  这项就是这些粒子所得到的动能
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  It's not that kinetic energy as seen
  这个动能并不是相对于
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  by somebody on the ground who is static,
  在地面上处于静态的某人
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  but by somebody riding with the center of mass.
  而是相对于与质心一起运动的某人
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  So, this is the kinetic energy relative to center of mass.
  因此这个动能是相对于质心的
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  We can give it some name.
  我们可以给它命个名